Association of simian virus 40 vp1 with 70-kilodalton heat shock proteins and viral tumor antigens.
Proper folding of newly synthesized viral proteins in the cytoplasm is a prerequisite for the formation of infectious virions. The major capsid protein Vp1 of simian virus 40 forms a series of disulfide-linked intermediates during folding and capsid formation. In addition, we report here that Vp1 is associated with cellular chaperones (HSP70) and a cochaperone (Hsp40) which can be coimmunoprecipitated with Vp1. Studies in vitro demonstrated the ATP-dependent interaction of Vp1 and cellular chaperones. Interestingly, viral cochaperones LT and ST were essential for stable interaction of HSP70 with the core Vp1 pentamer Vp1 (22-303). LT and ST also coimmunoprecipitated with Vp1 in vivo. In addition to these identified (co)chaperones, stable, covalently modified forms of Vp1 were identified for a folding-defective double mutant, C49A-C87A, and may represent a "trapped" assembly intermediate. By a truncation of the carboxyl arm of Vp1 to prevent the Vp1 folding from proceeding beyond pentamers, we detected several apparently modified Vp1 species, some of which were absent in cells transfected with the folding-defective mutant DNA. These results suggest that transient covalent interactions with known or unknown cellular and viral proteins are important in the assembly process.
Li
Peggy P
PP
Molecular Biology Institute, 456 Boyer Hall, University of California at Los Angeles, 611 East Charles E. Young Dr., Box 951570, Los Angeles, CA 90095-1570, USA.
Itoh
Noriko
N
Watanabe
Marika
M
Shi
Yunfan
Y
Liu
Peony
P
Yang
Hui-Jung
HJ
Kasamatsu
Harumi
H
D000818:Animals; D000957:Antigens, Viral, Tumor / Q000378:metabolism*; D002460:Cell Line; D002522:Chlorocebus aethiops; D050956:HSP40 Heat-Shock Proteins / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D047468:Immunoprecipitation; D017354:Point Mutation; D011485:Protein Binding; D017384:Sequence Deletion; D013539:Simian virus 40 / Q000502:physiology*; D017361:Viral Nonstructural Proteins / Q000378:metabolism; D015678:Viral Structural Proteins / Q000378:metabolism*; D019065:Virus Assembly
D000957:Antigens, Viral, Tumor; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D017361:Viral Nonstructural Proteins; D015678:Viral Structural Proteins